Binary Ethosomes As A Advanced Ethosomal System For Enhanced Drug Delivery: A Comprehensive Review

Abstract

Vesicular drug delivery systems have emerged as promising approaches to overcome the limitations associated with conventional dosage forms, particularly in topical and transdermal drug delivery. Ethosomes, lipid vesicles containing a high concentration of ethanol, have demonstrated superior skin permeation compared to classical liposomes. However, issues related to ethanol volatility and formulation instability have limited their broader application. To address these challenges, binary ethosomes have been developed as an advanced ethosomal system by incorporating a secondary alcohol, such as propylene glycol or isopropyl alcohol, along with ethanol. This modification enhances vesicle stability, drug entrapment efficiency, and skin permeation while reducing ethanol-related drawbacks. The present review critically analyzes binary ethosomes with respect to their composition, types, preparation methods, characterization techniques, mechanism of penetration, advantages, limitations, and pharmaceutical applications. Furthermore, future perspectives and challenges associated with the clinical translation of binary ethosomes are discussed.

Keywords

Binary ethosomes, ethosomal systems, vesicular drug delivery, transdermal delivery, topical drug delivery

Introduction

The development of novel drug delivery systems has become a central focus of pharmaceutical research due to the limitations associated with conventional dosage forms, such as low bioavailability, poor patient compliance, and systemic side effects [1,10–12]. Among various routes of administration, topical and transdermal drug delivery systems offer several advantages, including avoidance of first-pass metabolism, controlled drug release, reduced dosing frequency, and improved patient adherence [1,12].However, the stratum corneum, the outermost layer of the skin, acts as a major barrier, limiting the permeation of most therapeutic agents [11,12].To overcome this barrier, vesicular drug delivery systems have been extensively investigated [1,4,10,11].Liposomes were among the first vesicular carriers introduced; however, their limited skin penetration and stability issues restricted their effectiveness in transdermal delivery. Subsequently, modified vesicular systems such as niosomes, transfersomes, and ethosomes were developed to improve drug permeation and therapeutic efficacy [4,9,11].Ethosomes are soft, malleable lipid vesicles composed mainly of phospholipids, ethanol, and water [1,11].The high ethanol content imparts flexibility to the vesicular membrane and enhances drug permeation through the skin by disrupting the lipid structure of the stratum corneum [11,13]. Despite their promising characteristics, classical ethosomes suffer from drawbacks such as ethanol volatility, vesicle aggregation, and reduced stability during storage. To overcome these limitations, binary ethosomes were introduced as an advanced ethosomal system, incorporating an additional alcohol along with ethanol. This review aims to provide comprehensive overview of binary ethosomes, highlighting their role as an advanced vesicular carrier for enhanced drug delivery.

2. VESICULAR DRUG DELIVERY SYSTEMS

Vesicular drug delivery systems are colloidal carriers consisting of one or more concentric lipid bilayers enclosing an aqueous core. These systems are capable of encapsulating both hydrophilic and lipophilic drugs [1,4],thereby improving solubility, stability, and therapeutic efficacy.Liposomes are spherical vesicles composed of phospholipid bilayers but exhibit limited skin penetration due to their rigid structure [10]. Niosomes, formed from non-ionic surfactants, offer better stability but still face challenges in permeation efficiency. Transfersomes, also known as ultra-deformable vesicles, contain edge activators that enhance flexibility and penetration through narrow skin pores [4,9] .Ethosomes represent a significant advancement in vesicular systems due to their high ethanol content, which enhances membrane fluidity and skin permeation. Binary ethosomes further improve upon classical ethosomes by addressing their inherent limitations and enhancing overall performance.

3.ETHOSOMES: CONCEPT AND LIMITATIONS[2,3,5,8]

Ethosomes are lipid vesicles characterized by a high concentration of ethanol (20–45%), phospholipids, and water. Ethanol plays a dual role by increasing vesicle flexibility and enhancing skin permeation through lipid fluidization. Ethosomes have been successfully employed for the delivery of various drugs, including antifungal, anti-inflammatory, antiviral, and cosmetic agents [2,3,5,8] .Despite these advantages, classical ethosomes present several limitations

Ethanol volatility leading to instability during storage.

Vesicle aggregation and drug leakage.

Skin irritation at high ethanol concentrations.

Limited long-term stability.

These limitations prompted the development of modified ethosomal systems, including binary ethosomes. [17]

4. BINARY ETHOSOMES: DEFINITION AND COMPOSITION

Binary ethosomes are advanced ethosomal carriers formulated by incorporating a secondary alcohol in addition to ethanol. The secondary alcohol, such as propylene glycol, polyethylene glycol, or isopropyl alcohol, enhances vesicle stability, reduces ethanol evaporation, and improves drug permeation [11,13,17] .

4.1 COMPOSITION OF BINARY ETHOSOMES

The typical components of binary ethosomes include:

Phospholipids: Provide structural integrity and bilayer formation.

 Ethanol: Enhances membrane fluidity and skin permeation.

 Secondary Alcohol: Improves stability, hydration, and permeation.

 Aqueous Phase: Facilitates encapsulation of hydrophilic drugs.

 Drug Substance: Hydrophilic or lipophilic therapeutic agent. [1,4,11,17]

The synergistic action of ethanol and the secondary alcohol results in improved vesicular characteristics compared to classical ethosomes.

5. TYPES OF BINARY ETHOSOMES. [11,17]

Binary ethosomes can be classified based on:

Type of secondary alcohol used (propylene glycol-based, PEG-based, IPA-based systems)

Nature of drug encapsulated (hydrophilic or lipophilic drugs)

Intended route of delivery (topical or transdermal applications) [11,17]

Each type exhibits distinct physicochemical properties depending on formulation composition.

6. METHODS OF PREPARATION. . [11,17].

Binary ethosomes are commonly prepared using modified versions of traditional ethosomal preparation techniques.

6.1 Cold Method

In this method, phospholipids are dissolved in ethanol and secondary alcohol at room temperature. The aqueous phase is added slowly with continuous stirring to form vesicles.

6.2 Hot Method

Phospholipids are dispersed in water and heated, while ethanol and secondary alcohol are heated separately. Both phases are mixed under controlled conditions.

6.3 Thin Film Hydration Method

A thin lipid film is formed using organic solvents, followed by hydration with a hydroalcoholic solution containing ethanol and secondary alcohol.

7. CHARACTERIZATION OF BINARY ETHOSOMES.[1,3,11].

Binary ethosomes are evaluated using various physicochemical and biological parameters:

Vesicle Size and PDI: Determines homogeneity and stability.

Zeta Potential: Indicates surface charge and colloidal stability.

Entrapment Efficiency: Reflects drug loading capacity.

Morphological Analysis: SEM and TEM studies confirm vesicle structure.

In-vitro Drug Release: Evaluates release kinetics.

Ex-vivo Skin Permeation Studies: Assess penetration potential.

Stability Studies: Determine shelf-life and storage conditions.

8.MECHANISM OF SKIN PENETRATION[11,13,17].

The enhanced permeation of binary ethosomes is attributed to the synergistic effect of ethanol and secondary alcohol. Ethanol disrupts the lipid structure of the stratum corneum, while the secondary alcohol improves hydration and enhances drug solubility. The flexible vesicles penetrate deeper layers of the skin, releasing the drug in a controlled manner.

9. ADVANTAGES AND LIMITATIONS. [11,17]

9.1 Advantages

Enhanced skin permeation.

Improved formulation stability.

Higher drug entrapment efficiency.

Reduced ethanol-related volatility.

Suitable for a wide range of drugs.

9.2 Limitations

Potential skin irritation at high alcohol levels.

Complexity in formulation optimization.

Scale-up and manufacturing challenges.

10. PHARMACEUTICAL APPLICATIONS

Binary ethosomes have been explored for the delivery of:

Anti-inflammatory drugs.

Antifungal and antibacterial agents.

Antioxidants and cosmetic actives.

Transdermal systemic therapies.

These systems demonstrate superior therapeutic efficacy compared to conventional    formulations. [2,3,5,8,18,19].

FUTURE PERSPECTIVE

Future research should focus on clinical validation, optimization of alcohol ratios, large-scale manufacturing, and regulatory acceptance. Advance in formulation strategies may further enhance the potential of binary ethosomes in pharmaceutical and cosmetic industries. [11,12,17].

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